Atlantis heading home Friday – ISS/Chinese debris update

by Chris Bergin

Atlantis is set to start her cross-country piggyback ride back to Florida on Friday, returning back at KSC just as Endeavour starts rolling over to the Vehicle Assembly Building (VAB).

Meanwhile, further troubleshooting work has been taking place on the Russian computers onboard the International Space Station (ISS) – while the station didn’t need to carry out a Debris Avoidance Maneuver (DAM) to steer clear of Chinese debris created by the destroyed Fengyun 1C satellite.

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Atlantis is currently undergoing a level of post flight processing at the Edwards Air Force Base, following her return to Earth last Friday. Among the usual cleaning up of remaining propellants from the orbiter’s engines, engineers are carrying out a full repair to the port OMS Pod blanket – ahead of the flight – after the EVA-3 repaired joint came slightly loose during Friday’s return.

‘Took vehicle to MDD (Mate-Demate Device) at Dryden Friday around midnight, stacked and leveled vehicle Saturday. Current schedule is to be ready for ferry flight late Friday,’ noted Shuttle Standup/Integration report information on Monday evening.

‘Working aft access now. PRSD (Power Reactant Storage and Distribution), commodity safety and engine drying completed. Plan removal of blanket today from OMS pod, tap test and RTV ramping or other method OPO (Orbiter Project Office) chooses to cure the area. MDD and OPF (Orbiter Processing Facility) at KSC ready if ferry Friday.’

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Whether Atlantis’ ferry trip will take two or three days is still under discussion, with a final decision due on Thursday – which will include the planned airfields the duo will land at during their staggered flight to Florida.

‘Announcement for Ferry FRR (Flight Readiness Review) should come out today. Plan to review Thursday. Using SCA (Shuttle Carrier Aircraft) 905 at Dryden, and 932 will be pathfinder. DoD (Department of Defence) reports they have airfields to support ops,’ noted NASA information.

‘Nominal plan is three legs over two days, but have lots of daylight, so may be able to get vehicle to KSC in two days.’

Should the trip take three days, the SCA and Atlantis will be touching down at the Shuttle Landing Facility on the same day as Endeavour will be rolling over to the VAB ahead of August 7’s STS-118 launch. Endeavour is in the final stages of processing, head of her first launch in five years.

‘Plan to be ready to roll July 2, hook up sling and lift orbiter July 2, mate July 3. Expect plan from OPO on OMS pod TPS (Thermal Protection System) rework to support schedule this week,’ added Monday’s Standup report.

‘One tile cavity to bond. Nose landing gear work complete, and structural leak checks done over weekend. Planning payload bay door functional tonight (Monday) and final power down tomorrow (Tuesday).’

Back with Atlantis, and early indications point towards very little damage to her TPS, while reported notes about the apparently slow deployment of the right landing gear door, just prior to touchdown, appears to be a non issue.

‘Notes from runway report are: about 10 tiles with damage greater than one inch, frayed fibers on tadpole gap filler by arrowhead sticking out about 0.5 inch, gap filler noted late at LH (Left Hand) panel 21 on RCC appeared to stick out somewhat less than appeared on orbit, OMS pod blanket pulled up about an inch (less than was on orbit),’ added NASA information.

‘Were emails on weekend on whether RH landing gear door deployed slowly. Looked at this and don’t think is a problem, just some inherent differences between LH and RH (Right Hand) systems that can cause different rates of deployment. Will double-check data, but believe everything in spec.’

Meanwhile, on the ISS, Russian engineers are still trying to work out what caused the computer failure during Atlantis’ STS-117 mission. An attempt to restart the computers – this time without the by-pass jumpers in place – was unsuccessful, leading to Expedition 15 commander Fyodor Yurchikhin having to put the jumpers back in place to bring the computers back up again.

‘During his troubleshooting of the Russian Central Computer (TsVM) and Terminal Computer (TVM), Yurchikhin removed the secondary power supply bypass jumpers of the two TsVM1 & TVM2 data processing units (lanes), which are not in the controlling sets, and then attempted to restart the two lanes,’ noted ISS On Orbit status report information. The attempt was unsuccessful, and the by-pass jumpers were reconnected, awaiting further troubleshooting.’

Those computers, which – among other tasks – give the ISS to control attitude, has become even more important, following evaluations on Monday which noted the ISS will be travelling close to some of the Chinese debris, created by their anti-satellite test in January, which destroyed the aging Fengyun 1C satellite.

‘US and Russian ballistics experts are monitoring a conjunction with debris (Object 29719) from a Chinese satellite (Fengyun 1C), with TCA (Time of Closest Approach) Tuesday at 4:26pm EDT,’ added Monday’s On Orbit status report.

‘Currently predicted miss distance: 17 km. Further updates will determine the need for a DAM (Debris Avoidance Maneuver), with Go/No-Go decision (to be made). Time of ignition (TIG), if necessary: Tuesday afternoon at 2:10pm.

‘Solar Array Drag Reduction Delay: Implementation of the planned drag-reduction mode of off-pointing the US SAWs (Solar Array Wings) has been delayed until after the conjunction TCA to avoid adding to the prediction variables for the DAM analyses.’

However, further predictions, carried out on Tuesday, showed the threat wasn’t as big a problem as first thought.

“Probability of collision (Pc) with Object 29719, a piece of debris from a Chinese satellite (Fengyun 1C) went to zero as three consecutive conjunction predictions conducted by US and Russian Ballistics experts met all criteria for standing down from DAM (Debris Avoidance Maneuver),” noted Tuesday night’s On Orbit status report.

“Implementation of the planned drag-reduction mode of off-pointing the US SAWs (Solar Array Wings), delayed until after the conjunction, is now scheduled to begin Tuesday at 5:50pm EDT.”

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